Conventional antennas mounted to portable terminals are classified into a first type antenna which is mounted to the outside of a portable terminal, a second type antenna which is mounted on a printed wiring board (PWB) within a portable terminal, and a third type antenna which is mounted to an upper portion of a lengthwise section of a PWB within a portable terminal.
An example of the first type antenna is a dual band antenna disclosed in Japanese Patent Laid-Open No. 2004-56559. The first type antenna mounted to outside of a terminal has high-performance electric characteristics which are readily adjusted. An example of the second type antenna is a multi-band adaptive antenna apparatus disclosed in Japanese Patent Laid-Open No. 2008-118273. The second type antenna may be advantageously embedded in a terminal. The third type antenna may be advantageously made smaller than the second type antenna.
FIGS. 2A to 2E schematically illustrate the first to third type antennas. FIGS. 2A to 2B illustrate examples of the first type, FIG. 2C illustrates an example of the second type, and FIGS. 2D and 2E illustrate examples of the third type.
The three types of antennas have the above-discussed advantages, but have the following problems.
The first type antenna requires a large mounting volume outside a terminal. Therefore, in recent years when terminals tend to be made smaller, this type is difficult to use due to restriction on its design. The second type antenna mounted on a PWB has a large size, causing a problem in realizing a small-sized antenna. Therefore, the second type antenna cannot be used for a small-sized antenna. The third type antenna includes the electric characteristics that deteriorate due to a low impedance generated when it is made smaller or an increase in capacitive coupling.